Recent elevation changes of Svalbard glaciers derived from ICESat laser altimetry

We have tested three methods for estimating 2003-2008 elevation changes of Svalbard glaciers from multi-temporal ICESat laser altimetry: (a) linear interpolation of crossover points between ascending and descending tracks, (b) projection of near repeat-tracks onto common locations using Digital Elevation Models (DEMs), and (c) least-squares fitting of rigid planes to segments of repeat-track data assuming a constant elevation change rate. The two repeat-track methods yield similar results and compare well to the more accurate, but sparsely sampled, crossover points. Most glacier regions in Svalbard have experienced low-elevation thinning combined with high-elevation balance or thickening during 2003-2008. The geodetic mass balance (excluding calving front retreat or advance) of Svalbard's 34,600 km² glaciers is estimated to be −4.3 ± 1.4 Gt y⁻¹, corresponding to an area-averaged water equivalent (w.e.) balance of −0.12 ± 0.04 m w.e. y⁻¹. The largest ice losses have occurred in the west and south, while northeastern Spitsbergen and the Austfonna ice cap have gained mass. Winter and summer elevation changes derived from the same methods indicate that the spatial gradient in mass balance is mainly due to a larger summer season thinning in the west and the south than in the northeast. Our findings are consistent with in-situ mass balance measurements from the same period, confirming that repeat-track satellite altimetry can be a valuable tool for monitoring short term elevation changes of Arctic glaciers.     

IMPACT OF CHANGING HYDROLOGY ON NUTRIENT UPTAKE IN HIGH ARCTIC RIVERS

Despite the importance of river nutrient retention in regulating downstream water quality and the potential alterations to nutrient fluxes associated with climate‐induced changes in Arctic hydrology, current understanding of nutrient cycling in Arctic river systems is limited. This study adopted an experimental approach to quantify conceptual water source contributions (meltwater, groundwater), environmental conditions and uptake of NO₃^?, NH₄⁺, PO₄^3? and acetate at 12 headwater rivers in Svalbard and so determine the role of changing hydrology on nutrient uptake in these Arctic river systems. Most rivers exhibited low demand for NO₃^? and PO₄^3?, but demand for NH₄⁺ and acetate was more variable and in several rivers comparable with that measured in sub‐Arctic regions. The proportion of meltwater contributing to river flow was not significantly related to nutrient uptake. However, NH₄⁺ uptake was associated positively with algal biomass, water temperature and transient storage area, whereas acetate uptake was associated positively with more stable river channels. Mean demand for NH₄⁺ increased when added with acetate, suggesting NH₄⁺ retention may be facilitated by labile dissolved organic carbon availability in these rivers. Consequently, nutrient export from Arctic river systems could be influenced in future by changes in hydrological and environmental process interactions associated with forecasted climate warming. Copyright © 2013 John Wiley & Sons, Ltd.     

CARBONIFEROUS NON‐MARINE SOURCE ROCKS FROM SPITSBERGEN AND BJØRNØYA: COMPARISON WITH THE WESTERN ARCTIC

In this paper, we demonstrate that Carboniferous coaly and lacustrine strata have significant liquid hydrocarbon potential in an area extending from the Norwegian Barents Sea in the east to the Canadian Arctic in the west. Organic geochemical analyses were conducted on seven coals and coaly shales from the islands of Spitsbergen (Svalbard archipelago) and Bjørnøya (Norwegian Barents Sea). The results were interpreted in the context of published data from the two areas, and of time‐equivalent non‐marine successions on the Finnmark Platform (Norwegian Barents Sea), East Greenland, and the Sverdrup Basin (Canadian Arctic). In each of these areas, a warm and humid climate, together with the onset of rifting on the northern Pangea margin, facilitated the deposition and preservation of organic‐rich non‐marine sediments on a regional scale. All of the sediments have an elevated content of liptinitic macerals, dominated by alginite or sporinite. In the studied areas, the prolific younger source rocks which may be common in adjacent regions are often immature or absent. The identification of Carboniferous terrestrial strata with source rock potential may therefore enhance the petroleum potential of the studied regions.     

The thermal springs of Bockfjorden, Svalbard: II: selected aspects of trace element hydrochemistry

Waters from the Trollkjeldene (Troll springs) and Jotunkjeldene (Jotun springs) thermal springs on northern Svalbard have been analysed by ICP-AES, ICP-MS and IC techniques for a wide range of major and trace elements. Although it is plausible that the thermal waters originate from a deep reservoir in siliceous rocks, it appears that a significant component of their hydrochemical signature is derived from dissolution of higher-level Hecla Hoek marbles. Rare earth elements (REEs) show some degree of enrichment of heavy REEs in the water phase, relative to the marbles and to the travertines that precipitate from the waters. A strong positive Eu anomaly is also observed in the waters, suggesting preferential mobilisation of Eu under reducing conditions. The ratio Nb/Ta is rather well-preserved between the marbles, the waters and the travertines.     

MIGRATED PETROLEUM IN OUTCROPPING MESOZOIC SEDIMENTARY ROCKS IN SPITSBERGEN: ORGANIC GEOCHEMICAL CHARACTERIZATION AND IMPLICATIONS FOR REGIONAL EXPLORATION

The presence of migrated petroleum in outcropping rocks on Spitsbergen (Svalbard archipelago) has been known for several decades but the petroleum has not been evaluated by modern geochemical methods. This paper presents detailed organic geochemical observations on bitumen in outcrop samples from central and eastern Spitsbergen. The samples comprise sandstones from the Lower Cretaceous Carolinefjellet Formation, the Upper Triassic – Middle Jurassic Wilhelmøya Subgroup and the Upper Triassic De Geerdalen Formation; a limestone from the De Geerdalen Formation; and carbonates from the Middle Jurassic – Lower Cretaceous Agardhfjellet Formation. In addition a palaeo‐seepage oil was sampled from a vug in the Middle Triassic Botneheia Formation. This data is integrated with the results of analyses of C₁–C₄ hydrocarbon fluid inclusions trapped in quartz and calcite cements in these samples. Organic geochemical data suggest that the petroleum present in the samples analysed can be divided into two compositional groups (Group I and Group II). Group I petroleums have distinctive biomarker characteristics including Pr/Ph ratios of about 1.3–1.5, high tricyclic terpanes relative to pentacyclic terpanes, and relatively high methyl‐dibenzothiophenes compared to methyl‐phenanthrenes. By contrast Group II petroleums have low tricyclic terpanes relative to pentacyclic terpanes and low methyl‐dibenzothiophenes compared to methyl‐phenanthrenes, and most Pr/Ph ratios range from 1.90 to 2.57. The petroleum in both groups was derived from marine shale source rocks deposited in proximal to open marine settings. Group I petroleums, present in the sandstones of the Wilhelmøya Subgroup and the De Geerdalen Formation and as a palaeo‐seepage oil in the vug in the Botneheia Formation, are likely to have been sourced from the Middle Triassic Botneheia Formation. Group II petroleums, found in the sandstone of the Carolinefjellet Formation, the limestone from the De Geerdalen Formation and in carbonates of the Agardhfjellet Formation, are inferred to have been generated from the Jurassic‐Cretaceous Agardhfjellet Formation. The analysis of biomarker and aromatic hydrocarbons in the petroleums indicate three relative maturation levels, equivalent to expulsion at vitrinite reflectances of about 0.7–0.8%R_c, 0.8–0.9%R_c and 1.0–1.6%R_c. On average, Triassic host rocks contain petroleum of higher maturity compared to the Jurassic and Cretaceous host rocks. The fluid inclusion data suggest that gaseous hydrocarbons from the sandstones of the Wilhelmøya Subgroup are thermogenic, and are of similar maturity to the petroleum in extracts from these sandstones, suggesting that the gas was generated together with oil in the oil window. By contrast the inclusion gases from carbonate rocks analysed have a mixed (thermogenic / biogenic) origin. The outcropping rocks in which these oils occur are analogous to offshore reservoirs on the Norwegian Continental Shelf. The study may therefore improve our understanding of the subsurface offshore petroleum systems in the Barents Sea and possibly also in other circum‐Arctic basins.     

CHARACTERIZATION OF UPPER PALAEOZOIC ORGANIC‐RICH UNITS IN SVALBARD: IMPLICATIONS FOR THE PETROLEUM SYSTEMS OF THE NORWEGIAN BARENTS SHELF

Recent discoveries of hydrocarbons along the western margin of the Norwegian Barents Shelf have emphasised the need for a better understanding of the source rock potential of the Upper Palaeozoic succession. In this study, a comprehensive set of organic geochemical data have been collected from the Carboniferous – Permian interval outcropping on Svalbard in order to re‐assess the offshore potential. Four stratigraphic levels with organic‐rich facies have been identified: (i) Lower Carboniferous (Mississippian) fluvio‐lacustrine intervals with TOC between 1 and 75 wt.% and a cumulative organic‐rich section more than 100 m thick; (ii) Upper Carboniferous (Pennsylvanian) evaporite‐associated marine shales and organic‐rich carbonates with TOC up to 20 wt.%; (iii) a widespread lowermost Permian organic‐rich carbonate unit, 2–10 m thick, with 1–10 wt. % TOC; and (iv) Lower Permian organic‐rich marine shales with an average TOC content of 10 wt.%. Petroleum can potentially be tied to organic‐rich facies at formation level based on the gammacerane index, δ¹³C of the aromatic fraction and/or the Pr/Ph ratio. Relatively heavy δ¹³C values, a low gammacerane index and high Pr/Ph ratios characterize Lower Carboniferous non‐marine sediments, whereas evaporite‐associated facies have lighter δ¹³C, a higher gammacerane index and lower Pr/Ph ratios.     

Spatial and temporal variations of summer surface temperatures of high-arctic tundra on Svalbard — Implications for MODIS LST based permafrost monitoring

The ground surface temperature is one of the key parameters that determine the thermal regime of permafrost soils in arctic regions. Due to remoteness of most permafrost areas, monitoring of the land surface temperature (LST) through remote sensing is desirable. However, suitable satellite platforms such as MODIS provide spatial resolutions that cannot resolve the considerable small-scale heterogeneity of the surface conditions characteristic for many permafrost areas. This study investigates the spatial variability of summer surface temperatures of high-arctic tundra on Svalbard, Norway. A thermal imaging system mounted on a mast facilitates continuous monitoring of approximately 100 × 100 m of tundra with a wide variability of different surface covers and soil moisture conditions over the entire summer season from the snow melt until fall. The net radiation is found to be a control parameter for the differences in surface temperature between wet and dry areas. Under clear-sky conditions in July, the differences in surface temperature between wet and dry areas reach up to 10 K. The spatial differences reduce strongly in weekly averages of the surface temperature, which are relevant for the soil temperature evolution of deeper layers. Nevertheless, a considerable variability remains, with maximum differences between wet and dry areas of 3 to 4 K. Furthermore, the pattern of snow patches and snow-free areas during snow melt in July causes even greater differences of more than 10 K in the weekly averages. Towards the end of the summer season, the differences in surface temperature gradually diminish. Due to the pronounced spatial variability in July, the accumulated degree-day totals of the snow-free period can differ by more than 60% throughout the study area. The terrestrial observations from the thermal imaging system are compared to measurements of the land surface temperature from the MODIS sensor. During periods with frequent clear-sky conditions and thus a high density of satellite data, weekly averages calculated from the thermal imaging system and from MODIS LST agree within less than 2 K. Larger deviations occur when prolonged cloudy periods prevent satellite measurements. Furthermore, the employed MODIS L2 LST data set contains a number of strongly biased measurements, which suggest an admixing of cloud top temperatures.We conclude that a reliable gap filling procedure to moderate the impact of prolonged cloudy periods would be of high value for a future LST-based permafrost monitoring scheme. The occurrence of sustained subpixel variability of the summer surface temperature is a complicating factor, whose impact needs to be assessed further in conjunction with other spatially variable parameters such as the snow cover and soil properties.     

Congener-specific accumulation and patterns of chlorinated and brominated contaminants in adult male walruses from Svalbard, Norway: indications for individual-specific prey selection

Blubber samples from 17 adult, male walruses were sampled in eastern Svalbard and analyzed for chlorinated and brominated contaminants. A wide range of contaminants were detected, including PCBs (mean 2000; 95% range 1165-4005 ng/g lipid), DDE (mean 100: 95% range 50-310) ng/g lipid), chlordanes (mean 2500; 95% range 1347-5009) ng/g lipid, toxaphenes (mean 80; 95% range 51-132 ng/g lipid) and polybrominated diphenyl ethers (PBDEs) (mean 15 ng/g; 95% range 9-27 ng/g lipid). PCB and DDE levels were substantially lower than those of animals sampled 10 year earlier in this area, confirming a decreasing trend for these compounds in the Arctic. However, compared to other recently sampled marine mammals from Svalbard, walruses showed relatively high PCB and chlordane levels although they had lower levels of DDE, toxaphenes, and PBDEs, possibly due to species- and location-specific differences in exposure and metabolism. The range in contaminant levels found within the sample group was vast, despite the fact that the animals investigated were all adult males from the same location. The PCB pattern in highly contaminated animals was different from that in animals with low levels of contamination, with relatively more persistent PCBs in the highly contaminated group. This suggests that the more contaminated animals were feeding at higher trophic levels; possibly targeting seals in addition to mollusks as their prey. This suggestion was reinforced by the fatty acid profiles of the inner blubber layer of walruses with low versus high contaminant levels, which suggested different diets for the two groups.     

The thermal springs of bockfjord, svalbard: occurrence and major ion hydrochemistry

The Troll and Jotun thermal springs of northern Svalbard, with temperatures of up to 25.6°C, are derived from a major fault forming the junction between Devonian sandstones and Proterozoic marbles, mica schists and gneisses. The Troll waters are dominated by Na–HCO₃ compositions and the Jotun waters by Na–Cl compositions. The pristine thermal water source has a sub-neutral pH and is highly reducing. Taken at face value, common geothermometers suggest temperatures at depth of 130–180°C for the Troll springs (corresponding to a depth of 1.6–2.3 km), with 10–30% thermal water diluted by 70–90% cold water. Such geothermometers may, however, be inappropriate to the cool, high CO₂ waters of Bockfjord, and real temperatures at depth and dilution factors are probably considerably lower. The salinity of the thermal water appears to be only partially derived from water–rock interaction; Br\Cl ratios suggest that seawater or possibly evaporites may be a source of chloride salinity.